Patients screened for HDL cholesterol, apo A-I and Apo A-II levels. HDL turnover assessed in vivo to determine synthetic and catabolic rate of HDL apolipoproteins. Gel electrophoresis, immunoblotting and mass spectrometry to assess apolipoprotein and lipoprotein lipase structure with molecular DNA analysis where indicated. Nutritional perturbations of HDL metabolism assessed by restudying patients on a low fat diet.